1. Field of the Invention
This invention relates to a display device suitable for use for an extra large-sized display system used in a theater, a stadium, an assembly room and the like, and more particularly to such a large-sized display device which is capable of providing image displayed with high quality.
2. Description of the Prior Art
Conventionally, a large-sized fluorescent display panel such as, for example, an extra large-sized color television uses a number of picture cells planely arranged, each of which comprises a picture cell display tube generally constructed in such a manner as shown in FIG. 1.
More particularly, the picture cell display tube includes a multicolor luminous cell 1 comprising, for example, an illuminant 2 of red luminous color, an illuminant 3 of green luminous color and an illuminant 4 of blue luminous color 4 and having positive voltage of several KV applied thereto. At the rear of the luminous cell 1 are arranged cathodes 5 opposite to the illuminants 2, 3 and 4, respectively. The display tube also includes first control electrodes 6 and second control electrodes 7 interposed between the cathodes 5 and the luminous cell 1. The first control electrodes have applied thereto a control signal of positive several V and the second control electrodes have positive voltage of ten-odd V applied thereto. Thus, the luminous cell 1, cathodes 5 and control electrodes 6 and 7 constitute the picture cell display tube, which serves as one picture cell for a large-sized display panel such as a supertelevision.
When a large number of such picture cell display tubes are arranged in a plane to constitute picture cells for, for example, a supertelevision, the assembling of the picture cell display tubes one by one is highly troublesome; accordingly, the formation of display units each of which comprises a plurality of the picture cell display tubes is often employed in the assembling of a supertelevision.
FIG. 2 shows one example of such a display unit, wherein a plurality of the luminous cells 1 which are to be incorporated in each of a plurality of picture cell display tubes are arranged on a display plate 9, and the cathodes 5 and first and second control electrodes 6 and 7 arranged opposite to the luminous cells 1 are disposed in the respective compartments 11 formed in a unit casing 10; so that the display unit may be constituted.
A number of the so-formed display units 12, as shown in FIG. 3, are arranged in two directions to constitute a large-sized display panel, for example, such as an extra large-sized color television.
However, in such a display unit 12 constructed as described above described, a non-luminous region is formed around the luminous cells 1 for various reasons. More particularly, the display plate 9 is required to have a peripheral portion 14 acting as an overlap width with respect to a side plate 13 of the unit casing 10 in the connection of the display plate 9 to the unit casing 10, so that the upper and lower portions 15 of each of the luminous cells 1 may not be used as an anode due to an edge cooling phenomenon occurring at the upper and lower ends of the cathodes 5. Likewise, both side portions 16 of each of the luminous cells 1 cannot be used as an anode because the electron diffusion from the second control electrodes 7 does not reach these portions.
For such reasons as described above, a non-luminous region is produced at the peripheral portion of each of the luminous cells 1 formed on the display plate 9 to decrease the ratio of the effective area of the luminous cells 1 to the total area of the display plate 9 or luminous density, so that the dispersion of the picture cells may occur to cause the appearance of flickering of the picture cells.
In order to increase the luminous density, it might be conceived to arrange the picture cells as high a density as possible within an allowable range at the central portion of the display plate 9, excluding the periphery thereof. However, this causes the picture cells to be unevenly distributed, resulting in the non-uniform arrangement of the picture cells with respect to the overall display. Particularly, when a display panel is formed of a plurality of the display units arranged in two directions, the areas interposed between the respective adjacent display units 12 to surround the display units form a non-luminous region extending in two directions to produce a striped or checkered pattern on the display panel in the display operation. Thus, the quality of display is highly deteriorated to impair substantially the visibility of displayed image.
Further, as shown in FIG. 2, lead wires 17 for each of the picture cell display tubes must be laterally led out between the side plate 13 and a top plate 18 in view of the assembling of the display unit 12. Such construction, as shown in FIG. 3, requires gaps 20 to be provided between the respective adjacent display units 12 to lead out the lead wires 17 therethrough in the arrangement of a plurality of the display units for the production of a supertelevision or the like. Unfortunately, the gaps 20 are observed as black lines during the luminous operation of the luminous cells 1 to significantly deteriorate the visibility of the displayed image.